Waxes are a class of substances defined by their mechanical and physical properties. A substance mixture having the oil content indicated above is referred to in the sense of this invention as a wax and/or a soft wax if it is solid at a temperature above 10° C., in particular at greater than 25° C., e.g., from deformably soft to kneadable to breakable, and has a softening point of less than 65° C. (each at standard pressure, 1013 mbar). Waxes are also characterized by their oil content, melting point and/or viscosity.
Soft waxes having an oil content of more than 20 wt % have not previously been considered suitable for and/or in wood-based materials, e.g., as hydrophobizing agents, because their hydrophobizing effect is too low. This is true in particular if less than 0.5 wt % soft wax is added in relation to the amount of wood and/or wood constituents by weight.
The efficacy of the waxes as hydrophobizing agents depends very much on their chemical composition. For example, it is known that n-paraffins have a much stronger hydrophobizing effect than isoparaffins. Furthermore, reference is made to the publication by E. Roffael, E. Schriever, H.-A. May, “Hydrophobizing of Particleboard with Paraffin, Part 1: Findings and authors' Own Research,” Adhäsion 11 (1982), pp. 10-19, and to the publication by H.-A. May and E. Roffael, “Hydrophobizing of Particleboard with Paraffins,” Part 4 Adhäsion 28 (1, 2)17-21, according to which it was found that the hydrophobizing effect of paraffins increases with an increase in chain length in the range between C20 and C36. It is also known from this publication that the hydrophobizing effect becomes worse beyond a certain oil content.
See also FIG. 3 in W. E. Hsu, R. J. Melanson and P. J. Kozak, “The Effect of Wax Type and Content on Waferboard Properties” in Proceedings, Twenty-Fifth International Symposium on Particleboard and Composite Materials; 1990: pages 85-93, editor T. M. Maloney, Washington State University, W. A. Pullman.
U.S. Pat. No. 6,183,849 describes a method for producing composite boards in which the oil content of the wax is more than 30 wt % to 98 wt %. From the examples cited, the negative influence of using oil alone as a hydrophobizing agent is especially apparent. Wood-based materials containing wax with an oil content of 98% have a much greater swelling in thickness than do those containing a slack wax with an oil content of 17.6%.
WO 2004/065488-A1 proposes that oily waxes should be added to other waxes in such a way that the wax to be used as the hydrophobizing agent contains at least 21% n-paraffin.
It is known from SU 1613333 A1 that a mixture containing paraffin, borox, oleic acid, urea, kaolin, ammonium hexafluorosilicate, urea-formaldehyde resin, casein, water glass and water may be used for hydrophobizing OSB (oriented strandboard) in which the oil content of the paraffin used is 4% and its melting point is 72° C. According to SU-A1-1613333, a low-oil-content wax (4% oil content) that also contains urea is improved in its hydrophobizing effect by the addition of several other components, where the improvement in properties is not related to the urea addition. SU 1613333 A1 therefore does not relate to improving the hydrophobizing effect of soft wax having an oil content of greater than 20 wt %.
In extraction of oil from wax, fractions having a higher oil content are obtained. Since such high-oil-content soft waxes have a weak hydrophobizing effect, the object of the present invention was to improve the hydrophobizing effect of such soft waxes and to thereby make them available as hydrophobizing agents for wood-based materials. Waxes such as those obtained as high-oil-content “foots oils” or high-oil-content “slack wax” should be available for use as hydrophobizing agents in particular.